In comparison with a keypad and mouse, a touch screen as an input media provides a user with better convenience. Based on different implementation principles, touch screens may be classified into resistive touchscreens, capacitive touchscreens, surface acoustic wave touchscreens and infrared touchscreens and so on. Currently resistive and capacitive touchscreen technologies are widely used.
Mutual capacitive touch screens have the advantages of high sensitivity and multi-touch. The basic principle of mutual capacitive touchscreens is as follows: when a voltage is applied to a drive line, a signal change is detected from a detection line. The drive line determines a coordinate along an X direction and the detection line determines a coordinate along a Y direction. When detection is performed, X directional drive lines are scanned one by one. When each drive line is being scanned, signals on individual detection lines are read. In this way, every intersecting points of rows and columns may be scanned in one round, thus, X×Y signals are obtained totally. Such a detection method may determine coordinates of multiple points, thereby realizing multi-touch. An equivalent circuit of the detection method is illustrated in FIG. 1, wherein 101 represents a signal source, 102 represents a mutual capacitor between a drive line and a detection line, 103 represents a drive line resistor, 104 represents parasitic capacitors respectively formed between the drive line and a common electrode layer and between the detection line and the common electrode layer, 105 represents a detection line resistor, and 106 represents the detection circuit. When a finger touches the panel, a part of current flows to the finger, which is equivalent to a change in the mutual capacitance 102 between the drive line and the detection line. A small current change caused by such a change in the mutual capacitance may be detected at the detection terminal, and then a result whether the screen is touched is output.
In an Advanced Super Dimension Switch (ADS) touch screen integrating a capacitive touchscreen and a liquid crystal display, a transmitting electrode (TX) and a receiving electrode (RX) respectively have a large coupling capacitance with electrodes on an array substrate, such that liquid crystals will be deviated when the finger has not touched the liquid crystal screen yet. Deviation of liquid crystals will influence the touch detection. The uncertainty of liquid crystal deviation makes it impossible to distinguish between the differences caused by touch of the finger and the liquid crystal deviation, thereby leading to failure of detection.